Backlight Unit and Lcd Having the Same

ABSTRACT

Provided is a backlight unit. The backlight unit includes a frame, a light guide plate, a light absorption adhesive member, and a white light source. An opening is formed in the frame. The light guide plate is attached to the frame and formed larger than the opening. The light absorption adhesive member attaches the light guide plate to the frame and absorbs incident light. The white light source provides white light to the light guide plate.

TECHNICAL FIELD

The present invention relates to a backlight unit and a liquid crystaldisplay device having the same.

BACKGROUND ART

A cathode ray tube (CRT) has been widely used as one of display devicesfor displaying image data on a screen. However, the CRT has beeninconvenient for use because it has a large volume and a heavy weightfor its display area.

A thin flat display device, which has a slim profile and a large displayarea and thus can be used conveniently anywhere, has been developed andis gradually replacing the CRT.

A liquid crystal display device (LCD) is driven using characteristics ofliquid crystals, optical anisotropy and polarization. Since liquidcrystal molecules are long and thin, the alignment of liquid crystalmolecules has directivity. The alignment direction of the molecules maybe controlled by artificially applying electric field to liquidcrystals. Therefore, light can be transmitted or blocked according tothe direction alignment of the liquid crystal molecules through theoptical anisotropy of liquid crystals to display a color and an image.

Since the LCD cannot emit light by itself, it displays an image usinglight provided from an external light source or a backlight unit.

FIGS. 1 and 2 are an exploded perspective view and a partial enlargedview for illustrating a coupling structure of a light guide plate and aframe of a related art backlight unit.

Referring to FIGS. 1 and 2, the related art backlight unit includes aframe 10 and a light guide plate 20. A first recess 11 and a secondrecess 13 are formed at an inner side of the frame 10. The first andsecond recesses 11 and 13 are alternately formed and face differentdirections from each other. That is, the first recess 11 is formed on anupper surface of the frame 10, while the second recess 13 is formed onan under surface of the frame 10. A first protrusion 21 and a secondprotrusion 23 are formed at a side surface of the light guide plate 20.The first and second protrusions 21 and 23 are alternately formed andface different directions from each other. That is, the first protrusion21 is formed at an upper portion of the side surface of the light guideplate 20, while the second protrusion 23 is formed at an under portionof the side surface of the light guide plate 20.

In the backlight unit having the above-mentioned structure, the firstrecess 11 is coupled to the first protrusion 21 and the second recess 13is coupled to the second protrusion 23, and thereby coupling the frame10 to the light guide plate 20.

FIG. 3 is a view for illustrating a design criteria of a related artbacklight unit.

Referring to FIG. 3, the related art backlight unit may be divided intoa light guide plate region, a light emitting region, and an imagedisplay region. The light guide plate region may be defined by a widtha_(W) and a length a_(L) of the light guide plate, the light emittingregion may be defined by a width b_(W) and a length b_(L) of the lightemitting region, and the image display region may be defined by a widthc_(W) and a length c_(L) of the image display region. The image displayregion corresponds to an active region of the LCD.

The light emitting region is approximately 0.5 mm larger than the imagedisplay region. The light guide plate region is approximately 0.5 mmlarger than the light emitting region. An opening region in the middleof the frame 10 is approximately 0.05-0.1 mm larger than the light guideplate 20.

In a small-sized backlight unit having the above-mentioned structure,light emitted from a lateral side of the light guide plate 20 may bereflected on a sidewall of the frame 10 and be incident to the lightguide plate 20. Here, light of a band shape delicately shows on an outeredge of the light emitting region due to light reflected on thesidewall.

Also, the light guide plate having a thickness of 0.3 mm or smaller hasbeen required, but it is difficult to form protrusions for coupling sucha thin light guide plate to a frame. Although the protrusions areformed, they may be broken due to their frangibility. When theprotrusions are broken, the broken pieces move into the light emittingregion to affect image display.

DISCLOSURE OF INVENTION Technical Problem

An embodiment of the present invention provides a backlight unit capableof stably coupling a frame to a thin light guide plate and preventingtransmission caused by light emitted from a lateral side of the lightguide plate, reflected on a sidewall of the frame, and incident to thelight guide plate.

An embodiment of the present invention is to provide a liquid crystaldisplay device and a mobile communication terminal that can bemanufactured in a slim type by having a backlight unit capable of stablycoupling a frame to a thin light guide plate and preventing transmissioncaused by light emitted from a lateral side of the light guide plate,reflected on a sidewall of the frame, and incident to the light guideplate.

Technical Solution

An embodiment of the present invention provides a backlight unitcomprising: a frame including an opening; a light guide plate attachedto the frame and formed larger than the opening; a light absorptionadhesive member attaching the light guide plate to the frame andabsorbing incident light; and a white light source providing white lightto the light guide plate.

An embodiment of the present invention provides a backlight unitcomprising: a frame including an opening; a light guide plate attachedto the frame and formed larger than the opening; an adhesive memberformed between the light guide plate and the frame; a colored lightsource providing colored light to the light guide plate; and afluorescent excitation sheet formed on the light guide plate to emitcolored light incident through the light guide plate as white light.

An embodiment of the present invention provides a liquid crystal displaydevice comprising: a backlight unit including a frame including anopening, a light guide plate attached to the frame and formed largerthan the opening, a light absorption adhesive member attaching the lightguide plate to the frame and absorbing incident light having color, anda white light source providing white light to the light guide plate; anda liquid crystal panel receiving light from the backlight unit todisplay an image.

An embodiment of the present invention provides a liquid crystal displaydevice comprising: a backlight unit including a frame including anopening, a light guide plate attached to the frame and formed largerthan the opening, an adhesive member formed between the light guideplate and the frame, a colored light source providing colored light tothe light guide plate, and a fluorescent excitation sheet formed on thelight guide plate to emit colored light incident through the light guideplate as white light; and a liquid crystal panel receiving light fromthe backlight unit to display an image.

An embodiment of the present invention provides a mobile communicationterminal comprising: a backlight unit including a frame including anopening, a light guide plate attached to the frame and formed largerthan the opening, a light absorption adhesive member attaching the lightguide plate to the frame and absorbing incident light having color, anda white light source providing white light to the light guide plate; aliquid crystal panel receiving light from t he backlight unit to displayan image; a communication unit performing a communication with theoutside; and a control unit controlling the backlight unit, the liquidcrystal panel, and the communication unit.

An embodiment of the present invention provides a mobile communicationterminal comprising: a backlight unit including a frame including anopening, a light guide plate attached to the frame and formed largerthan the opening, an adhesive member formed between the light guideplate and the frame, a colored light source providing colored light tothe light guide plate, and a fluorescent excitation sheet formed on thelight guide plate to emit colored light incident through the light guideplate as white light; a liquid crystal panel receiving light from thebacklight unit to display an image; a communication unit performing acommunication with the outside; and a control unit controlling thebacklight unit, the liquid crystal panel, and the communication unit.

Advantageous Effects

According to a backlight unit of the embodiment, a frame can be stablycoupled to a thin light guide plate and transmission can be prevented,which is caused by light emitted from a lateral side of the light guideplate, reflected on a sidewall of the frame, and incident to the lightguide plate.

According to a backlight unit of the embodiment, an assembling processthereof can be automated.

According to a liquid crystal display device and a mobile communicationterminal of the embodiment, they can be manufactured in a slim type byhaving a backlight unit capable of stably coupling a frame to a thinlight guide plate and preventing transmission caused by light emittedfrom a lateral side of the light guide plate, reflected on a sidewall ofthe frame, and incident to the light guide plate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are an exploded perspective view and a partial enlargedview for illustrating a coupling structure of a light guide plate and aframe of a related art backlight unit;

FIG. 3 is a view for illustrating design criteria of a related artbacklight unit;

FIGS. 4 and 5 are a bottom perspective view and a sectional view forillustrating a coupling structure of a light guide plate and a frame ofa backlight unit according to an embodiment of the present invention;

FIG. 6 is a sectional view of a backlight unit according to anotherembodiment of the present invention;

FIG. 7 is a schematic view of an LCD according to an embodiment of thepresent invention; and

FIG. 8 is a schematic view of an LCD according to another embodiment ofthe present invention.

MODE FOR THE INVENTION

It will be understood that when a layer (or film), a region, patterns,or a structure is referred to as being ‘on’ or ‘under’ another layer (orfilm), region, or patterns, it can be directly on the other layer (orfilm), region, or patterns, or intervening layers may also be present.

An embodiment of the present invention will be described below in detailwith reference to the accompanying drawings.

FIG. 4 is a bottom perspective view for illustrating a couplingstructure of a light guide plate and a frame of a backlight unitaccording to an embodiment of the present invention, and FIG. 5 is across-sectional view taken along a line I-I of FIG. 4.

Referring to FIGS. 4 and 5, the backlight unit according to anembodiment of the present invention includes a frame 110, a light guideplate 120, an adhesive member 130, and a light emitting part 140. Anopening A is formed in the frame 110, and the light guide plate 120 isformed larger than the opening A. The adhesive member 130 is formed on arim of the frame 110 and attaches the light guide plate 120 to the frame110. The light emitting part 140 is formed at one end of the frame 110to provide light.

FIGS. 4 and 5 illustrates the coupling structure of the light guideplate 120 and the frame 110. A shape of the frame 110 may be variouslychanged, and an object for receiving light, for example, a liquidcrystal panel, may be disposed over the frame 110.

The adhesive member 130 may be selected from a two-sided adhesive tape,silicon, and epoxy. The light guide plate 120 according to an embodimentof the present invention is attached to the frame 110 using the adhesivemember 130, and thus may be formed to a small thickness. For example,the light guide plate 120 may be formed to a thickness of 0.3 mm orsmaller, and may be stably attached to the frame 110 using the adhesivemember 130.

The light guide plate 120 may be 1.5-2.0 mm larger than a light emittingregion of the light guide plate 120. Therefore, according to thebacklight unit of the embodiment, light reflected on a side surface ofthe frame 110 can be prevented from being incident to the light emittingregion of the light guide plate 120. This can prevent transmission on anouter edge of the light emitting region of the light guide plate 120caused by the light reflected on the side surface of the frame 110.

In an embodiment of the backlight unit having the above-mentionedstructure, a light source may be used as the light emitting part 140,and a light absorption adhesive member may be used as the adhesivemember 130.

The light absorption adhesive member including color can absorb lightincident from the light emitting part 140. The light absorption adhesivemember can more effectively prevent light reflected on a side surface ofthe frame 110 from being incident to the light emitting region of thelight guide plate 120. Therefore, this can prevent transmission on anouter edge of the light emitting region of the light guide plate 120caused by the light reflected on the side surface of the frame 110. Thelight absorption adhesive member may be selected from a two-sidedadhesive tape, silicon, and epoxy.

The light emitting part 140 provides white light to the light guideplate 120, and for example, may be a light emitting diode. The lightemitting part 140 may include red/green/blue light emitting diodes or awhite light emitting diode.

Next, a backlight unit according to another embodiment of the presentinvention will be described with reference to FIG. 6. FIG. 6 illustratesa backlight unit that employs a colored light source and a fluorescentexcitation sheet.

Referring to FIG. 6, the backlight unit according to another embodimentof the present invention includes a frame 310, a light guide plate 320,an adhesive member 330, and a fluorescent excitation sheet 350. Also,the backlight unit includes a colored light source as a light emittingpart.

The light guide plate 320 is attached to the frame 310 using theadhesive member 330. The light guide plate 320 is formed larger than anopening C of the frame 310. The light guide plate 320 may be 1.5-2.0 mmlarger a light emitting region of the light guide plate 320. Therefore,according to the backlight unit of the present invention, lightreflected on a side surface of the frame 310 can be prevented from beingincident to the light emitting region of the light guide plate 320.

The adhesive member 330 having color may absorb light incident from thecolored light source. The adhesive member 330 can more effectivelyprevent light reflected on a side surface of the frame 310 from beingincident to the light emitting region of the light guide plate 320.Accordingly, this can prevent transmission on an outer edge of the lightemitting region of the light guide plate 320 due to the light reflectedon the side surface of the frame 310.

The colored light source provides colored light to the light guide plate320, and for example, may be a light emitting diode. The colored lightsource may emit blue light and the fluorescent excitation sheet 350 mayinclude a yellow fluorescent material or red/green fluorescentmaterials. Alternatively, the colored light source may emit blue/greenlight, and the fluorescent excitation sheet 350 may include a redfluorescent material. Here, the fact that the fluorescent excitationsheet 350 includes a fluorescent material means that the fluorescentmaterial is included inside the fluorescent ex citation sheet 350 or iscoated outside the fluorescent excitation sheet 350.

The fluorescent excitation sheet 350 emits colored light incident fromthe colored light source as white light. A position of the fluorescentexcitation sheet 350 may be changed depending on a shape of the frame310. FIG. 6 illustrates a coupling structure of the light guide plate320 and the frame 310. The shape of the frame 310 may be variouslychanged, and an object for receiving light, for example, a liquidcrystal panel may be disposed over the frame. The fluorescent excitationsheet 350 is disposed between the light guide plate 320 and an objectfor receiving white light, for example, a liquid crystal panel.

The backlight unit having the above-mentioned structure can facilitatethe automation of an assembling process of a frame and a light guideplate. The automation of the assembling process can reduce a unit cost.

The above-described backlight unit may be applied to an LCD and makes itpossible to manufacture a slim-sized LCD. FIGS. 7 and 8 are schematicviews of an LCD according to an embodiment of the present invention.

Referring to FIG. 7, an LCD according to an embodiment of the presentinvention includes a backlight unit 410, a prism sheet 420, and a liquidcrystal panel 430. The backlight unit 410 includes the backlight unitdescribed with reference to FIGS. 4 to 6. The prism sheet 420concentrates light emitted from the backlight unit 410 into the liquidcrystal panel 430. The liquid crystal panel 430 may display an imageusing light incident through the prism sheet 420.

Referring to FIG. 8, an LCD according to another embodiment of thepresent invention includes a backlight unit 510, a transflectivepolarizing prism sheet 520, and a liquid crystal panel 530. Thebacklight unit 510 includes the backlight unit described with referenceto FIGS. 4 to 6. The transflective polarizing prism sheet 520concentrates light emitted from the backlight unit 510 into the liquidcrystal panel 530. The liquid crystal panel 520 may display an imageusing light incident through the transflective polarizing prism sheet520.

The transflective polarizing prism sheet 520 transmits light that ispolarized to a predetermined direction and reflects light that is notpolarized thereto. For example, the transflective polarizing prism sheet520 may have a transmission axis parallel to a transmission axis of apolarizer attached to a rear surface of the liquid crystal panel 530. Inthat case, the polarized light is transmitted through the transflectivepolarizing prism sheet 520 to be incident to the liquid crystal panel530 such that the polarized light is transmitted trough the polarizerattached to the liquid crystal panel 530. Light reflected on thetransflective polarizing prism sheet 520 may is reflected on componentsdisposed thereunder, and some of the reflected light may be transmittedthrough the transflective polarizing prism sheet 520 to be incident tothe liquid crystal panel 530. Accordingly, when using the transflectivepolarizing prism sheet 520, the brightness can be improved by more than30% compared to use of a commonly used prism sheet. An upper surface ofthe transflective polarizing prism sheet 520 is formed in a prism shape.

The above-described backlight unit or LCD may be applied to a mobilecommunication terminal, and a slim type mobile communication terminalcan be realized. The mobile communication terminal according to anembodiment of the present invention may include the backlight unitdescribed with reference to FIGS. 4 to 6. Also, the mobile communicationterminal according to an embodiment of the present invention may includethe LCD described with reference to FIGS. 7 and 8.

The mobile communication terminal according to an embodiment of thepresent invention includes a communication unit for a communication withthe outside. The mobile communication terminal according to anembodiment of the present invention includes a control unit thatcontrols the communication unit and the backlight unit or the LCD.

INDUSTRIAL APPLICABILITY

According to a backlight unit of an embodiment of the present invention,a frame can be stably coupled to a slim type light guide plate andtransmission on an outer edge of a light emitting region can be prevent,which is caused by light emitted lateral side of the light guide plate,reflected on a side surface of the frame, and incident to the lightguide plate.

According to a backlight unit of an embodiment of the present invention,an assembling process thereof can be automated.

An LCD and a mobile communication terminal according to an embodiment ofthe present invention can be formed in a slim type by having a backlightunit by stably coupling a frame to a slim type light guide plate andpreventing transmission on an outer edge of a light emitting regioncaused by light emitted lateral side of the light guide plate, reflectedon a side surface of the frame, and incident to the light guide plate.

1. A backlight unit comprising: a frame including an opening; a lightguide plate attached to the frame and formed larger than the opening; alight absorption adhesive member attaching the light guide plate to theframe and absorbing incident light; and a white light source providingwhite light to the light guide plate.
 2. The backlight unit according toclaim 1, wherein the light absorption adhesive member having color isselected from a two-sided adhesive tape, silicon, and epoxy.
 3. Thebacklight unit according to claim 1, wherein the thickness of the lightguide plate is 0.3 mm or smaller.
 4. The backlight unit according toclaim 1, wherein the light guide plate, is 1.5-2.0 mm larger than alight emitting region of the light plate to prevent light reflected on aside surface of the frame from being incident to the light emittingregion of the light guide plate.
 5. A backlight unit comprising: a frameincluding an opening; a light guide plate attached to the frame andformed larger than the opening; an adhesive member formed between thelight guide plate and the frame; a colored light source providingcolored light to the light guide plate; and a fluorescent excitationsheet formed on the light guide plate to emit colored light incidentthrough the light guide plate as white light.
 6. The backlight unitaccording to claim 5, wherein the adhesive member is selected from atwo-sided adhesive tape, silicon, and epoxy.
 7. The backlight unitaccording to claim 5, wherein the adhesive member absorbs incident lighthaving color.
 8. The backlight unit according to claim 5, wherein thethickness of the light guide plate is 0.3 mm or smaller.
 9. Thebacklight unit according to claim 5, wherein the light guide plate, is1.5-2.0 mm larger than a light emitting region of the light guide plateto prevent light reflected on a side surface of the frame from beingincident to the light emitting region of the light guide plate.
 10. Thebacklight unit according to claim 5, wherein the colored light sourceemits a blue light and the fluorescent excitation sheet includes ayellow phosphor or red/ green fluorescent materials.
 11. The backlightunit according to claim 5, wherein the colored light source emitsblue/green lights and the fluorescent excitation sheet includes a greenfluorescent material.
 12. A liquid crystal display device comprising: abacklight unit including a frame including an opening, a light guideplate attached to the frame and formed larger than the opening, a lightabsorption adhesive member attaching the light guide plate to the frameand absorbing incident light having color, and a white light sourceproviding white light to the light guide plate; and a liquid crystalpanel receiving light from the backlight unit to display an image. 13.The liquid crystal display device according to claim 12, comprising aprism sheet formed between the backlight unit and the liquid crystalpanel.
 14. The liquid crystal display device according to claim 12,comprising a transflective polarizing prism sheet formed between thebacklight unit and the liquid crystal panel.
 15. A liquid crystaldisplay device comprising: a backlight unit including a frame includingan opening, a light guide plate attached to the frame and formed largerthan the opening, an adhesive member formed between the light guideplate and the frame, a colored light source providing colored light tothe light guide plate, and a fluorescent excitation sheet formed on thelight guide plate to emit colored light incident through the light guideplate as white light; and a liquid crystal panel receiving light from the backlight unit to display an image.
 16. The liquid crystal displaydevice according to claim 15, comprising a prism sheet formed betweenthe backlight unit and the liquid crystal panel.
 17. The liquid crystaldisplay device according to claim 15, comprising a transflectivepolarizing prism sheet formed between the backlight unit and the liquidcrystal panel.
 18. A mobile communication terminal comprising: abacklight unit including a frame including an opening, a light guideplate attached to the frame and formed larger than the opening, a lightabsorption adhesive member attaching the light guide plate to the frameand absorbing incident light having color, and a white light sourceproviding white light to the light guide plate; a liquid crystal panelreceiving light from t he backlight unit to display an image; acommunication unit performing a communication with the outside; and acontrol unit controlling the backlight unit, the liquid crystal panel,and the communication unit.
 19. The mobile communication terminalaccording to claim 18, comprising a prism sheet formed between thebacklight unit and the liquid crystal panel.
 20. The mobilecommunication terminal according to claim 18, comprising a transflectivepolarizing prism sheet formed between the backlight unit and the liquidcrystal panel.
 21. A mobile communication terminal comprising: abacklight unit including a frame including an opening, a light guideplate attached to the frame and formed larger than the opening, anadhesive member formed between the light guide plate and the frame, acolored light source providing colored light to the light guide plate,and a fluorescent excitation sheet formed on the light guide plate toemit colored light incident through the light guide plate as whitelight; a liquid crystal panel receiving light from the backlight unit todisplay an image; a communication unit performing a communication withthe outside; and a control unit controlling the backlight unit, theliquid crystal panel, and the communication unit.
 22. The mobilecommunication terminal according to claim 21, comprising a prism sheetformed between the backlight unit and the liquid crystal panel.
 23. Themobile communication terminal according to claim 21, comprising atransflective polarizing prism sheet formed between the backlight unitand the liquid crystal panel.